Process and system for controlling a windshield wiper, particulary for a motor vehicle

Abstract

A process and a system for controlling a windshield wiper, in particular on a motor vehicle, in which a rain sensor is located on the glass to be wiped and within the region of the windshield wiper. The sensor outputs a sensor signal as a function of the amount of moisture. The signal is detected periodically and, when a reference degree of moisture is reached during a measurement cycle, the system produces a triggering signal and the windshield wiper is activated. The wiping process takes place even when the windshield wiper is wetted with moisture only to a slight but nevertheless disturbing extent. In the process, when a degree of moisture below a reference degree of moisture is present at the end of the measurement cycle, this degree of moisture is included additively to the degree of moisture of a further measurement cycle. Thereupon, the degree of moisture of the further measurement cycle is compared with the reference degree of moisture.

I claim: 
     
       1. A method for controlling a windshield wiper, including a windshield wiper on a motor vehicle, comprising the steps of placing a rain sensor on a windshield in a region of the windshield to be wiped by a wiper, the sensor outputting a sensor signal as a function of an amount of moisture on the windshield;   detecting the sensor signal periodically during a succession of measurement cycles to provide a succession of detected sensor signals;   summing the sensor signals detected in each of the succession of measurement cycles, a sum of the detected sensor signals indicating a degree of moisture;   upon reaching a degree of moisture in a measurement cycle equal or greater than a reference degree of moisture, producing a triggering signal for controlling the windshield wiper;   upon occurrence of a degree of moisture below the reference degree of moisture within a measurement cycle which includes a present degree of moisture, establishing an initial degree of moisture equal to a fraction of the present degree of moisture;   summing the initial degree of moisture to the degree of moisture of a subsequent measurement cycle to obtain a summation of moisture degrees; and   comparing the resulting summation of degree of moisture with the reference degree of moisture for producing a wiper triggering signal.   
     
     
       2. A method according to claim 1, wherein the summation of degree of moisture serves as a starting value of a further measurement cycle.   
     
     
       3. A method according to claim 2, wherein the starting value is formed as a function of the summation of degree of moisture.   
     
     
       4. A method according to claim 3, wherein the starting value is derived as a percentage of the summation of the degree of moisture.   
     
     
       5. A method according to claim 1, wherein the degree of moisture of a first measurement of a series of measurements is represented by the instantaneous sensor signal.   
     
     
       6. A method according to claim 1, wherein, after a plurality of measurements, the degree of moisture is represented by the sum of the increments in moisture.   
     
     
       7. A method according to claim 3, wherein the starting value is formed only after a delay time from a previous measurement has been exceeded.   
     
     
       8. A method for controlling a windshield wiper, including a windshield wiper on a motor vehicle, comprising the steps of: placing a rain sensor on a windshield region of the windshield to be wiped by a wiper, the sensor outputting a sensor signal as a function of an amount of moisture on the windshield;   detecting the sensor signal periodically during a succession of measurement cycles to provide a succession of detected sensor signals;   summing the sensor signals detected in each of the succession of measurement cycles, a sum of the detected sensor signals indicating a degree of moisture;   upon reaching a degree of moisture in a measurement cycle equal or greater than a reference degree of moisture, producing a triggering signal for controlling the windshield wiper; and   wherein, upon an occurrence of a degree of moisture below the reference degree of moisture at the end of a measurement cycle, producing a triggering signal upon the presence of the degree of moisture within a given interval of time.   
     
     
       9. A method according to claim 8, further comprising a step of starting the windshield wiper when the degree of moisture in a measurement cycle at the end of the given time interval is a part of the reference degree of moisture.   
     
     
       10. A method according to claim 9, wherein the degree of moisture is represented by the sum of increments in measurements of moisture.   
     
     
       11. A system for operating a windshield wiper, including a windshield wiper on a motor vehicle, comprising: a sensor of intensity of rain located on a windshield in a region of the windshield to be wiped by the wiper, the sensor outputting a sensor signal as a function of an amount of moisture on the windshield;   a computer, and an analog/digital converter connecting said sensor to said computer; and   wherein said computer is operative in accordance with a program providing a process comprising the steps of:   detecting the sensor signal periodically during a succession of measurement cycles to provide a succession of detected sensor signals;   summing the sensor signals detected in each of the succession of measurement cycles, a sum of the detected sensor signals indicating a degree of moisture;   upon reaching a degree of moisture in a measurement cycle equal or greater than a reference degree of moisture, producing a triggering signal for controlling the windshield wiper;   upon occurrence of a degree of moisture below the reference degree of moisture within a measurement cycle which includes a present degree of moisture, establishing an initial degree of moisture equal to a fraction of the present degree of moisture;   summing the initial degree of moisture to the degree of moisture of a subsequent measurement cycle to obtain a summation of moisture degrees; and   comparing the resulting summation of degrees of moisture with the reference degree of moisture.   
     
     
       12. A system according to claim 11, wherein the sensor is a resistive moisture sensor.